Method of controlling the fatty acid content of cooking fats or cooking oils

ABSTRACT

An adjustable continuous filtration system; a continuous split-stream bypass filtration system; a method for controlling the proportion of a fluid recycled through a filtration system; a method for controlling the proportion of a fluid which is routed to the filter of a filtration system, and the proportion of the fluid which is discharged from the system without passing through the filter; and a method for controlling the quality of cooking fats and cooking oils. The mechanisms for controlling the proportion of fluid routed or recycled to a filter depend on the size or width of orifices in passageways conveying the fluid, including the restriction of one or more of the orifices. A needle valve beneficially provides a continuous range of variation of orifice size. If the quality of cooking fat or cooking oil discharged from the filtration system is below industry standards, the proportion of the cooking fat or cooking oil routed or recycled to the filter is increased. If the quality of the discharged cooking fat or cooking oil is appreciably above industry standards, the proportion of the cooking fat or cooking oil routed or recycled to the filter is decreased.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.09/206,204 filed on Dec. 5, 1998, now abandoned, which was acontinuation-in-part of U.S. patent application Ser. No. 09/010,272filed on Jan. 21, 1998, now U.S. Pat. No. 5,846,409.

BACKGROUND OF THE INVENTION

The present invention relates to filtration. More particularly, theinvention relates to a filtration system for quality control of cookingfats and cooking oils.

In the culinary industry filtration is generally employed to purify usedcooking fats and cooking oils. In the absence of such purification,impurities build up in the fats and oils to a level which isunacceptable by industry standards.

As fats and oils are used in cooking, they tend to break down, degrade,and hydrolyze to free fatty acids, glycerol, and other polar products.The free fatty acids are among the more harmful products of thisdegradation. The recommended maximum acceptable level for free fattyacids is three to four percent.

The prior art discloses filtration systems for removing such impuritiesfrom cooking fats and cooking oils; see, e.g., U.S. Pat. Nos. 5,597,601,4,747,944, 3,667,613, 5,247,876, 3,107,601, 2,698,092, and 3,630,361.What is lacking, however, is a filtration system which is adjustable inaccordance with the quality of the cooking fat or cooking oil which isbeing filtered. The present invention provides such a system.

More specifically, the prior art fails to provide filtration apparatusin which a predetermined portion of the cooking fat or cooking oil isrecycled or routed to the filtration system before being dischargedtherefrom. For example, U.S. Pat. No. 4,747,944 to George discloses afiltration system in which filtrate is recirculated by being dischargedinto a vessel which contains unfiltered cooking fat or cooking oil. Themixture of partially-filtered fat or oil is then returned to the filter.An obvious drawback of this system is the absence of any mechanism forcontrolling the proportion of the fat or oil which is recycled to thefilter. A second apparent limitation is the requirement of a vessel formixing the liquid discharged from the filter with untiltered liquid.

British Patent 751,892 discloses a filtration system for mineral oil.The system includes a part-flow filter cartridge which controls theproportion of mineral oil which is recycled to a filter. It will beapparent to those skilled in the art that this control mechanism lacksflexibility with regard to varying the proportion of fluid which isrouted or recycled to the filter. This limitation is particularlyserious with regard to the desirability of continuous variation of theproportion of fluid which is recycled, or which is routed to the filterbefore being discharged from the filtration system.

SUMMARY OF THE INVENTION

In general, the present invention in a first aspect provides anadjustable continuous recycle filtration system. The filtration systemcomprises a filter; means for conveying a fluid to the filter; means forrecycling a portion of the fluid to the filter; and means forcontrolling the proportion of the fluid which is recycled to the filterby controlling the size of an orifice in a passageway through which thefluid flows.

A first embodiment of the adjustable recycle filtration system comprisesa filter; means for pressurizing a fluid to be conveyed to the filter; afirst passageway for receiving the pressurized fluid from thepressurization means; a second passageway for receiving fluid dischargedfrom the filter; means for lowering the pressure in the secondpassageway below the pressure in the first passageway; a thirdpassageway connected to the pressure-lowering means; a fourth passagewayconnected to the third passageway and to the filter; a fifth passagewayconnected to the third and fourth passageways; a sixth passageway fordischarging fluid from the fifth passageway; and an orifice restrictiondisposed between the fifth and sixth passageways, for controlling therate of flow of the fluid through the fourth, fifth, and sixthpassageways. The first, second, third, fourth, fifth, and sixthpassageways, the pressure-lowering means, and the orifice restrictionare constructed and arranged so that fluid discharged from the thirdpassageway is split into a first stream flowing through the fourthpassageway and a second stream flowing through the fifth passageway, andthe proportion of fluid which is recycled to the filter before beingdischarged through the sixth passageway is controlled and determined bythe size of an orifice in the orifice restriction between the fifth andsixth passageways.

A second embodiment of the adjustable recycle filtration systemcomprises a filter; a first passageway which provides an inletpassageway for a fluid to be conveyed to the filter; a second passagewaywhich provides a passageway for fluid discharged from the filter; meansfor lowering the pressure in the second passageway below the pressure inthe first passageway; a third passageway connected to thepressure-lowering means; a fourth passageway connected to the thirdpassageway and to the filter; a fifth passageway interconnecting thethird and fourth passageways; and an orifice restriction disposed in thethird passageway, for controlling the rate of flow through the fourthand fifth passageways; the first, second, third, fourth, and fifthpassageways, the pressure-lowering means, and the orifice restrictionbeing constructed and arranged so that fluid discharged from the thirdpassageway is split into a first stream flowing through the fourthpassageway and a second stream flowing through the fifth passageway, andthe proportion of the fluid which is recycled to the filter before beingdischarged through the fifth passageway is controlled and determined bythe size of an orifice in the orifice restriction disposed in the thirdpassageway.

A third embodiment of the adjustable recycle filtration system comprisesa filter; means for pressurizing a fluid to be conveyed to the filter; afirst passageway for receiving the pressurized fluid from thepressurization means; a second passageway for receiving fluid dischargedfrom the filter; a third passageway connected to the pressure-loweringmeans; a fourth passageway connected to the third passageway and to thefilter; and a fifth passageway connected to the third and fourthpassageways, for discharging fluid from the filtration system. Thefirst, second, third, fourth, and fifth passageways, and thepressure-lowering means are constructed and arranged so that fluiddischarged from the third passageway is split into a first streamflowing through the fourth passageway and a second stream flowingthrough the fifth passageway, and the proportion of the fluid which isrecycled to the filter before being discharged from the fifth passagewayis controlled and determined by the widths of the orifices in the fourthand fifth passageways.

In a second aspect the present invention provides an adjustablecontinuous bypass filtration system. A first embodiment thereofcomprises a filter; means for pressurizing a fluid to be conveyed to thefilter; a first passageway for receiving the pressurized fluid from thepressurization means; a second passageway for receiving fluid dischargedfrom the filter; means for lowering the pressure in the secondpassageway below the pressure in the first passageway; a thirdpassageway connecting the first passageway and the filter to oneanother; a fourth passageway connected to the first and thirdpassageways; a fifth passageways for discharging fluid from the fourthpassageway; and an orifice restriction disposed in the third passageway,for controlling the rate of flow of the fluid through the third, fourth,and fifth passageways. The pressure-lowering means are disposed betweenand interconnect the second, the fourth, and fifth passageways. Thesecond passageway connects the pressure-lowering means and the filter toone another. The first, second, third, fourth, and fifth passageways,the pressure-lowering means, and the orifice restriction are constructedand arranged so that fluid discharged from the first passageway is splitinto a first stream flowing through the third passageway and a secondstream flowing through the fourth passageway, and the proportion of thefluid which is routed to the filter before being discharged through thefifth passageway is controlled and determined by the size of an orificein the orifice restriction disposed in the third passageway.

A second embodiment of the adjustable bypass filtration system comprisesa filter; a first passageway for conveying a fluid to the filter; asecond passageway for discharging fluid from the filter; means forlowering the pressure in the second passageway below the pressure in thefirst passageway; a third passageway connecting the first passageway andthe filter to one another; a fourth passageway connected to the firstand third passageways; a fifth passageway for discharging the fluid fromthe fourth passageway; and an orifice restriction disposed in the fourthpassageway, for controlling the rate of flow of the fluid through thethird, fourth, and fifth passageways; the pressure-lowering means beingdisposed between the fourth and fifth passageways, the second passagewayinterconnecting the pressure-lowering means, the filter, and the fourthpassageway; the first, second, third, fourth, and fifth passageways, thepressure-lowering means, and the orifice restriction being constructedand arranged so that fluid discharged from the first passageway ispartitioned into a first stream flowing through the third passageway anda second stream flowing through the fourth passageway, and theproportion of the fluid which is routed to the filter or is dischargedfrom the system is controlled and determined by the size of an orificein the orifice restriction disposed in the fourth passageway.

A third embodiment of the adjustable bypass filtration system comprisesa filter; a first passageway for conveying a fluid to the filter; asecond passageway for discharging fluid from the filter; means forlowering the pressure in the second passageway below the pressure in thefirst passageway; a third passageway connecting the first passageway andthe filter to one another; a fourth passageway connected to the firstand third passageways; and a fifth passageway for discharging the fluidfrom the fourth passageway; the pressure-lowering means being disposedbetween the fourth and fifth passageways, the second passagewayinterconnecting the pressure-lowering means, the filter, and the fourthpassageway; the first, second, third, fourth, and fifth passageways, andthe pressure-lowering means being constructed and arranged so that fluiddischarged from the first passageway is partitioned into a first streamflowing through the third passageway and a second stream flowing throughthe fourth passageway, and the proportion of the fluid which is routedto the filter or is discharged from the system is controlled anddetermined by the size of orifices in the third and fourth passageways.

In a fourth embodiment of the adjustable bypass filtration system,orifice restrictions are provided in both third and fourth passageways.

A fifth embodiment of the adjustable bypass filtration system comprisesa filter; a first passageway which provides an inlet passageway for afluid to be conveyed to the filter or to be discharged from the system;a second passageway which provides a passageway for fluid dischargedfrom the filter; a third passageway connected to the first passagewayand to the filter; a fourth passageway interconnecting the first andsecond passageways; an orifice restriction disposed in the fourthpassageway, for controlling the size of an orifice in the fourthpassageway; and a fifth passageway for discharging fluid from the fourthpassageway; whereby the fluid discharged from the second passageway issplit into a first stream flowing through the third passageway to thefilter and a second stream flowing through the fourth passageway to bedischarged through the fifth passageway, and the proportion of the fluidwhich is routed to the filter or which is discharged through the fifthpassageway is controlled and determined by the size of an orifice in theorifice restriction disposed in the fourth passageway.

The direction of fluid flow through the filter can be reversed ifreverse flow through the filter should be desired or required.

In a third aspect the invention provides a method for controlling thequality of cooking fats and cooking oils. The method comprises providinga filter for filtering the cooking fats or cooking oils; routing orrecycling a portion of a cooking fat or a cooking oil to the filter; andcontrolling the proportion of the cooking fat or the cooking oil whichis routed or recycled to the filter before being discharged. Thedischarged cooking fat or cooking oil is analyzed for quality control.If the quality of the discharged cooking fat or cooking oil is belowindustry standards, the proportion of the cooking fat or cooking oilwhich is recycled is increased. If the quality of the discharged cookingfat or cooking oil is appreciably above industry standards, theproportion of the cooking fat or cooking oil which is recycled isdecreased.

In a fourth aspect the invention provides a method for controlling theproportion of fluid recycled through a filtration system. The methodcomprises providing a filter for filtering the fluid; pressurizing thefluid for conveyance to the filter; conveying the pressurized fluid tothe filter; recycling a portion of the fluid to the filter; andcontrolling the proportion of the fluid which is recycled to the filterbefore being discharged from the system by controlling the size of anorifice in a passageway through which the fluid flows.

In a fifth aspect the invention provides a method for controlling theproportion of a fluid which is routed to the filter of a filtrationsystem, and the proportion of said fluid which is discharged from thesystem without passing through the filter. The method comprisesproviding a filter for filtering the fluid; conveying a portion of thefluid to the filter through a first passageway; discharging the filteredfluid and a portion of the unfiltered fluid through a second passageway;and controlling the proportions of the fluid flowing through the firstand second passageways by disposing an orifice restriction in the firstor in the second passageway.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a first embodiment of anadjustable continuous recycle filtration system, made in accordance withthe principles of the present invention.

FIG. 1-A is a schematic representation of a second embodiment of anadjustable continuous recycle filtration system, made in accordance withthe principles of the present invention.

FIG. 2 is a schematic representation of a first embodiment of anadjustable continuous bypass filtration system, made in accordance withthe principles of the present invention.

FIG. 2-A is a schematic representation of a second embodiment of anadjustable continuous bypass filtration system, made in accordance withthe principles of the present invention.

FIG. 2-B is a schematic representation of a third embodiment of anadjustable continuous bypass filtration system, made in accordance withthe principles of the present invention.

FIG. 3 is a schematic representation of a portion of a fourth embodimentof an adjustable continuous bypass filtration system, made in accordancewith the principles of the present invention.

FIG. 4 is a schematic representation of a second embodiment of anadjustable continuous recycle filtration system, made in accordance withthe principles of the present invention.

FIG. 5 is a schematic representation of a fourth embodiment of anadjustable continuous bypass filtration system, made in accordance withthe principles of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

More specifically, reference is made to FIG. 1, in which is shown afirst embodiment of an adjustable continuous recycle filtration system,made in accordance with the principles of the present invention, andgenerally designated by the numeral 10.

A pump 1 discharges a fluid into line 7. An ejector 2 creates a partialvacuum in line 11, and/or lowers the pressure in line 11 below that inline 7. Fluid discharged from the ejector 2 is split into first andsecond streams which flow through lines 8 and 9, respectively. Fluid inline 8 enters a container 13 filled with a filter medium 14, percolatesor diffuses therethrough, and after passing through a particle-retainingscreen 4 exits through line 11 and is recycled to the ejector 2. Anorifice restriction 3 between lines 9 and 12 controls the rate of fluidflow through lines 8, 9, and 12 by imposing a pressure drop across theorifice restriction 3. By varying the size of the orifice, the rates offlow through lines 8, 9, and 12 can be varied as much as desired. Thus,when the pressure drops across the container 13 and the orificerestriction 3 are equal, the rate of flow through line 8 is the same asthrough lines 9 and 12. By increasing the restriction, i.e. bydecreasing the size of the orifice between lines 9 and 12, a slower rateof flow is obtained through lines 9 and 12 than through line 8. Theopposite effect is achieved by decreasing the restriction, i.e byincreasing the size of the orifice between lines 9 and 12, so that moreof the partially-filtered fluid is discharged through line 12 than isrecycled to the container 13 through line 8. Preferably, the orificerestriction 3 is constructed and arranged to enable continuous variationof the degree of restriction without interrupting the flow to change oradjust the orifice-restriction device. One means of so doing is to use avalve, preferably a needle valve, as the orifice restriction 3.

Reference is now made to FIG. 1-A, in which is shown a second embodimentof an adjustable continuous recycle filtration system, made inaccordance with the principles of the present invention, generallydesignated by the numeral 10A. In this embodiment the orificerestriction 3 is disposed in line 8 rather than in line 9. The functionof the orifice restriction 3 remains the same; viz., to control therates of flow through lines 8 and 9, thereby controlling the proportionof fluid recycled to the filter 13.

Reference is now made to FIG. 2, in which is shown a first embodiment ofan adjustable continuous bypass filtration system, made in accordancewith the principles of the present invention, and generally designatedby the numeral 20.

The adjustable continuous bypass filtration system 20 comprises a filter13; a pump 1; a first passageway 7 connected to the pump 1; a secondpassageway 11 for receiving fluid discharged from the filter 13; anejector 2 for lowering the pressure in the second passageway 11 belowthe pressure in the first passageway 7; a third passageway 8 connectingthe first passageway 7 and the filter 13 to one another; a fourthpassageway 9 connected to the first 7 and third 8 passageways; a fifthpassageway 12 for discharging fluid from the fourth passageway 9; and anorifice restriction 3 disposed in the third passageway 8, forcontrolling the rate of flow of the fluid through the third 8, fourth 9,and fifth 12 passageways. The ejector 2 is disposed between andinterconnects the second 11, fourth 9, and fifth 12 passageways. Thefluid discharged from the first passageway 7 is split into a firststream flowing through through the third passageway 8, and a secondstream flowing through the fourth passageway 9. The proportion of thefluid which is routed to the filter 13 via the third passageway 8 beforebeing discharged through the fifth passageway 12 is controlled anddetermined by the size of an orifice in the orifice restriction 3disposed in the third passageway 8. The proportion of the fluid flowingthrough the third passageway 8 to the filter 14 is increased by openingorifice 3 if the free fatty-acid content of the fluid discharged throughthe fifth passageway 12 is above industry standards; and the proportionof the fluid flowing through the third passageway 8 to the filter 14 isdecreased by closing the orifice 3 if the free fatty-acid content of thefluid discharged through the fifth passageway 12 is below industrystandards.

Reference is now made to FIG. 2-A, in which is shown a second embodimentof an adjustable continuous bypass filtration system, made in accordancewith the principles of the present invention, and generally designatedby the numeral 20A. In this embodiment the orifice restriction 3 isdisposed in the fourth passageway 9 instead of in the third passageway8. The function of the orifice restriction 3 is the same for bothembodiments 20 and 20A; viz., to control the proportions of fluid routedto the filter 13 via the third passageway 8 and to the fourth passageway9, from which it is discharged through the fifth passageway 12.

Reference is now made to FIG. 2-B, in which is shown a third embodimentof an adjustable continuous bypass filtration system, made in accordancewith the principles of the present invention, and generally designatedby the numeral 20B. In this embodiment there are no orifice restrictions3, and the proportion of fluid which is conveyed to the filter 13through the third passageway 8 and to the fourth passageway 9 isdetermined by the size of orifices in the third passageway 8 and fourthpassageway 9.

Reference is now made to FIG. 3, in which is shown a portion of a fourthembodiment of an adjustable continuous bypass filtration system, made inaccordance with the principles of the present invention. In this fourthembodiment, orifice restrictions 3 are provided in lines 8 and 9, andthe ejector 2 interconnects lines 9, 11, and 12.

Reference is now made to FIG. 4, in which is shown a second embodimentof an adjustable recycle filtration system, made in accordance with theprinciples of the present invention, and generally designated by thenumeral 30. The second embodiment 30 of the filtration system is similarto the first embodiment 10 shown in FIG. 1, except that in the secondembodiment 30 the orifice restriction 3 and line 12 are omitted from thesystem. In the second embodiment 30, the proportion of fluid recycled tothe filter 13 is controlled and determined by the sizes of orifices inlines 8 and 9.

Reference is now made to FIG. 5, in which is shown a fifth embodiment ofan adjustable continuous bypass filtration system, made in accordancewith the principles of the present invention, and generally designatedby the numeral 40. This embodiment differs from the second embodiment20A thereof shown in FIG. 2-A by omission and absence of the ejector 2.

In preferred embodiments of the present invention, the adjustablecontinuous filtration systems are used to filter and/or purify usedcooking fats and cooking oils. For this purpose the cooking fat orcooking oil being discharged from the filtration system is tested forquality control, to determine whether it satisfies the specifications ofthe industry. If the discharged cooking fat or cooking oil is not withinthe specifications, the proportion of the cooking fat or cooking oilbeing routed or recycled through line 8 is increased. If the fat or oiltests far better than is required by the specifications, the rate offlow through line 8 is decreased. If purification other than filtrationis needed, an adsorbent is added to or substituted for the filter medium14. Since fats are by definition solid at room temperature, heat and/orthermal insulation are/is supplied or provided to maintain the fats in aliquid state while circulating in and through the filtration system.

It is to be understood that, if desired, a filter press or filter leafcould be used instead of a container filled with a filter medium. Suchsubstitution would in no way affect the basic concept of the presentinvention. Moreover, instead of an ejector, any other means of loweringthe pressure in line 11 would suffice, and would lie within the scope ofthe present invention. The use of an ejector is, however, clearlyadvantageous and is to be preferred, because it provides a compact meansfor so doing which is simpler, requires less space, and comprises nomoving parts as compared, e.g., to a vacuum pump or a vacuum line.

Many restaurants continue to use their cooking fats and cooking oilswell beyond the recommended maximum 3-4% fatty-acid content. This isprimarily because, until recently, there has been no accurate, simple,and rapid method for determining the percentage of free fatty acidstherein. There is now, however, an analytical method which is simple,quick, and accurate. This method is preferred for determining the freefatty-acid content of cooking fats and cooking oils in combination withthe filtration/purification systems and methods herein described. Themethod is described in detail in U.S. Pat. No. 5,620,897 to Zappe, whichis hereby incorporated by reference.

The term “fluid” includes liquids, vapors, and gases. While thepreferred embodiments of the present invention utilize liquid cookingfats and cooking oils as the filtrand, the apparati and methods are byno means limited or restricted in scope to the filtration and/orpurification of liquids, and include the filtration and purification ofvapors and gases to remove, e.g., particulate solids therefrom.

Moreover, it will be apparent to those skilled in the art that themethod of analyzing cooking fats and cooking oils, and adjusting theproportion thereof routed or recycled to the filter 13 is applicable tofluids in general, and the extension of this method to fluids generallyis within the scope of the present invention.

I claim:
 1. A method for controlling quality of a fluid which is to bepurified, the method comprising the steps of: (a) providing a filter forfiltering the fluid; (b) conveying a first portion of unfiltered fluidto the filter through a first passageway; (c) discharging filtered fluidfrom the filter and a second portion of unfiltered fluid through asecond passageway; (d) controlling proportions of the fluid flowingthrough the first and second passageways; (e) analyzing the fluiddischarged through the second passageway by determining acid content ofthe fluid; (f) increasing the proportion of fluid flowing through thefirst passageway which is conveyed to the filter if the acid content ofthe fluid discharged through the second passageway is above industrystandards; and (g) decreasing the proportion of the fluid flowingthrough the first passageway which is conveyed to the filter through thefirst passageway if the acid content of the discharged fluid isappreciably below industry standards.
 2. A method for controllingquality of a fluid which is to be purified, the method comprising thesteps of: (a) providing a filter for filtering the fluid; (b) conveyinga first portion of unfiltered fluid to be filtered to the filter througha first passageway; (c) discharging filtered fluid from the filter and asecond portion of unfiltered fluid through a second passageway; (d)controlling proportions of the fluid flowing through the first andsecond passageways; (e) analyzing the fluid discharged through thesecond passageway by determining free fatty-acid content of the fluid;(f) increasing the proportion of fluid flowing through the firstpassageway which is conveyed to the filter if the free fatty-acidcontent of the fluid discharged through the second passageway is aboveindustry standards; and (g) decreasing the proportion of the fluidflowing through the first passageway which is conveyed to the filterthrough the first passageway if the free fatty-acid content of thedischarged fluid is appreciably below industry standards.